Wireless system



J. MILLS AND J. R. CARSON.

WIRE LESS SYSTEM.

APPLICATION FILED OCT-6.1915.

Patented July 8, 1919.

2 SHEETS-SHEET 1.

J. MILLS AND J. R. CARSON.

WIRELESS SYSTEM.

APPLICATION FILED OCT. 6. I915.

Patented July 8, 1919.

2 SHEETSSHEET -2.

INVENTORS Jail/21115115 gfdzrzfiarsm I z 2 I r t I.

\ ATTORNEYS JOHN R. CARSON, residing UNITED STATES PATE T OFFICE. H

JOH miLLs, F WYOMING, NEW JERSEY, A D JOHN R. CARSON, OF NEW YoEK, N. Y.,

ASSIG-NORS 'ro AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORA- TION OF NEW YORK.

WIRELESS SYSTEM.

To all whom it may concern:

Be it known that we, JOHN Mums; and I at Wyoming, in the county of Essex and btate of New Jersey, and at New York, in the county of New York and State of New York, respectively, have invented certain Improvements in Wireless Systems, of which the following is a s ecification.

his invention relates to a wireless system and more particularly to a wireless system which is designed for duplex operation. Its object is to provide means for protecting the receiving instrument of a wlreless system from disturbing oscillations and, in particular, to embody such protective means in a system designed for duplex operation, whereby the receiving instrument is protected both against static disturbances and disturbances arising from the transmitting portion of such duplex system.

It is well known that in wireless telegraphy and telephony the magnitude of the transmitted current is enormously greater than the received current, their ratio sometimes being of the order of one million to one. This enormous ratio renders inapplicable to wireless systems duplex methods which have been successfully employed in wire telegraph and telephone systems.

It is further well known that static or atmospheric interference not only constitutes a serious menace to the successful commercial operation of wireless systems, but also that its elimination presents a very diflicult problem. This difficulty inheres in the fact that c the natural or characteristic oscillations, set up in a receiving system by a static disturbance, are of substantially the frequency to most strongly affect the receiving device, and that, therefore, static interference cannot be tuned out by a change of wave length, as can. persistent interference from a foreign sending station. As regards the elimination of static interference, this invention does not attempt to reduce or eliminate the radio-frequency natural oscillations, but, by interposing detectors between a receiving device and the seat of said radio-frequency oscillations, resultant low frequency oscillations are developed which by a combination of circuits are balanced out with respect to said receiving device. In the several embodiments of the invention in duplex systems, it is contemplated that the system be resonantly responsive to two frequencies,

Specification of Letters Patent.

one of which is that of the signals to be received and the other is that at which signals are transmitted.

The invention may best be understood by reference to the accompanying drawings in which Figuresl and 2 are diagrams showing two different embodiments of the invent1on, and Figs. 8, 4 and 5 are diagrams showing different embodiments of the invention in a receiving system with duplex features omitted. I

Referring to Fig. 1, 1 is an antenna for the radiation and reception of energy, said antenna containing the primary of an oscillation transformer 30, which couples said antenna with the transmitting apparatus, conventionally represented by a high frequency generator 29. The antenna system has a plurality of branches in parallel, said antenna being grounded through three parallel branch circuits 2, 3 and 4. The branch circuit 4, which may be termed the transmission branch circuit, is tuned to resonance at the transmission frequency, and said branch circuit therefore offers a very low impedance to currents of said frequency. Branch circuit 4 contains a tuning inductance 13, a tuning condenser 14, and an anti-resonant set 8 which is tuned to'anti-resonance at the reception frequency. The branch circuit 2', which may be termed the reception branch circuit, contains a tuning condenser 10, a coupling coil 9, and a set 5 which is adjusted for anti-resonance at the transmission frequency. By means of said tuning con denser and said coupling coil the circuit consisting of the antenna 1 in series with the branch circuit 2 is tuned to resonance at the frequency of reception. It will thus be understood that circuit 2 offers a very high impedance to the transmission currents and is adjusted for maximum response to the signals to be received. Branch circuit 3, which may be termed the auxiliary branch circuit, contains a coupling coil 11,a tuning condenser 12, and two sets 6 and 7, the first of which is anti-resonant to the reception frequency and the second of which is anti-resonant to the transmission frequency. The branch circuit 3, therefore, offers a very high impedance Patented July 8, 191 9.- Application filed October 6, 1915. Serial No. 54.392.

both to currentof transmission and current I of reception wave length. It is'evident that a the organization thus far described has a plurality of degrees of freedom and that as a whole it is resonantly responsive to two frequencies one of which is the "frequency of transmission and the other of which is the frequency of reception. It is further evident that the circuit consisting of the antenna in series with, branch 2 is resonant at the reception frequency, while the circuit consistmg of the antenna in series with branch 4 as well 22, 22, preferably of the vacuum tube type,

detectors 19 and 19, also preferably of the vacuum tube type, and the loosely coupled oscillation circuits 15 and 15. The same characters, with and without primes, refer to corresponding, similar elements, those without primes, denoting elements connected to the branch 2, and those-with primes denoting corresponding and similar elements connected to the branch 3. The oscillation circuit 15 contains a coupling coil 16, a condenser 18, and a resistance element 17, and is tuned to the frequency of-reception. The circuit 15 correspondingly contains the elements 16, 18 and 17 and is tuned to the frequency to which the branch 3 is responsive. 20, 23, 20, 23 represent high inductance impedance elements, while 21,24,21,34' represent non-inductive resistance elements.

The operation of 'the organization shown in Fig. 1 will now be explained. Considering first the phenomena of transmission, it has been already stated that branch 4 offers a very low impedance to the transmission currents, while branches 2 and 3 are substantially anti-resonant at the transmission frequency; it therefore follows that practically all the transmission current flows through the branch 4, and only a very small fraction thereof through branches 2 and 3. However, owing to the enormous ratio of the trans mitted and received currents, the fraction of the transmission current flowing through the branch 2, if only one part in one hundred thousand of the total transmission current, will still be much greater than the current excited by electromagnetic waves from the communicating station. It will be seen then, that, in spite of its high impedance to the transmitted current, the oscillation circuit 15 may be excited more strongly by the said transmission current than by the relatively very small reception current to which 15.is

tuned to respond. Except for the branch 3 and its associated apparatus, it may well be that, in spite of careful design and sharp anti-resonance, the currents set up in the receiver 26 by the transmission urrent, will be prohibitively large. One'of t e functions of branch 3 and its associated apparatus is, however, to substantially eliminate the transmission interference in a manner now to be explained. Since branches 2 and 3 both contain elements or sets which are'anti-resonant at the transmission frequency, they offer substantially the same impedance to the transmission currents. Therefore approximately equal fractions of the transmission current flow through branches 2 and 3, and these fractional currents are of substantially the same phase.- The oscillation circuits 15 and 15' are, therefore, excited by equal induction from branches 2 and 3, respectively, and the effects of the current in circuits 15 and 15' after translation and amplification oppose and may be made to substantially neutralize with respect to the receiver 26. When this condition is attained, it is evident that no current corresponding to the transmission current flows through the receiver 26, and therefore the organization satisfies the fundamental condition for duplex operation, namely freedom from transmission interference.

As regards now the phenomena attending the reception of signals from the communicating station (not shown), it is evident that, by virtue of the anti-resonance of branches 1 and 3 to the reception frequency, the system is essentially the same as though branches 1 and 3 were removed, leaving the antenna grounded through branch 2 alone. As has already been stated, the circuit consisting of the antenna in series with branch 2 and the oscillation circuit 15 are separately tuned to the reception frequency. Therefore circuit 15 oscillates strongly in response to the received signals, while circuit 15' oscilates very feebly. -The current, then, corresponding to said received signals and flowing through the receiver 26, is essentially independent of the presence of branch 3 andits associated apparatus as well as of branch 4, and hence the arrangement shown 110 is such as to satisfy the condition of efficient reception of signals.

The operation ofthe organization shown in Fig. l in reducing static interference is as follows: When the receiving system as a 1 15 whole is excited by a static disturbance it oscillates in its characteristic or natural modes of damped oscillations. The predominant oscillation excited by the static disturbance in circuit 15 is practically deter- 120 mined as regards periodicity and damping by the electrical constants of said circuit,

that is by the values of its inductance, ca-

pacity and resistance elements. Similarly the corresponding oscillation of circuit 15 125 is determined by the electrical constants of said circuit. The predominant oscillations occurring in circuits l5 and 15 will be of different frequencies, since said circuits are tuned to different frequencies; but such os- 130 cillations may be made tohave the same damping factors by assigning suitable values to the inductance and reslstance elements of said circuits. If the said damping pressed on resistances 24 and 24 are equal fractional and similar, the resultant current in the receiver 26 is zero. These voltages may be made equal in a number of ways, such as by proportioning the relative amplifying powers of the amplifiers 22 and 22, or the relative values of the resistance elements 24 and 24, or the relative values of the inductances 9 and, 11. As regards static elimination, the embodiment of the invention shown in Fig. l contemplates having the receiving device operatively connected to two parallel antenna branches, the said receiving device being so connected to said parallel vbranches that the high frequency natural oscillations, after translation by detectors or after translation and amplification, oppose and substantially neutralize with respect to said receiving device. It will be understood further that, while thereceiving device is operatively connected through detectors, the order of translation and amplification is immaterial, and, indeed, that though amplifiers are desirable they are not is the elimination of interference. A minor same time factors in order that the natural oscillations executed by said circuits shall have the same dampiing. To this end it is necessary that when R and L are the resistance andinductance respectively of circuit 15 and R and L the resistance and inductance respectively of circuit 15.

A second embodiment of the invention: is shown in Fig. 2, which will be readily understood from the foregoing explanation of the organization shown in Fig. 1. As regards the antenna 1, the branches 2, 3 and 4, the detectors, the amplifiers, and the receivers, the arrangement of Figs. 1 and 2 are identical. The diflerence between the two structures is that in Fig. 2 the oscillation circuits 25 and 25 corresponding to oscillation circuits 15 and 15 of Fig. 1, are inductively coupled to both branches 2 and 3. The advantage of this arrangement lies in the fact that since, as already explained, arts of the transmission current of essentia ly the same amplitude and phase flow through branches 2 and 3, the result-ant- If particularly strong protection is re quired from transmission interference, the oscillation circuits 15 and 15 of Fig. 1 and 25 and 25 of Fig. 2 may include sets which are anti-resonant to the transmission wave length, as shown in Fig. 2, in which 27 and 27 represent sets anti-resonant to currents of the transmission frequency.

Certain features of the invention, as regards static elimination, are not limited to a combination designed for duplex operation. Fig. 3 shows one embodiment of the invention in a receiving system alone. It will be understood by reference to the drawings that the structure shown in Fi .3 is the same essentially as that shown inFig 1 with the omission in Fig. 3 of component parts whose functions relate to duplex operation: Such component parts are the trans mitting system proper, branch circuit 4 and the anti-resonant sets 5, 7 and 8 of Fig.1. As in Fig. 1 branch circuit 2 is the reception branch circuit and the branch circuit 3 is the auxiliary branch circuit whose function and non-essential structural difference between the two organizations is the mode in which the receiver 26 is coupled to the output side of amplifiers 22 and 22. In Fig. 3, said receiver is shown as difi'erentially coupled by repeat coils 28 and 28, preferably designed for operation at telephonic frequencies. The operation of the organization shown in Fig. 3 in eliminating static interference is precisely the same as that ofthe organization shown in Fig. 1 heretofore described.

By omitting the duplex features of Fig. 2, the structure becomes that shown in Fig. 4. The operation of the system shown in Fig. 4 and the protection afiorded the receiving instrument against static disturbances will, therefore, be readily understood from the foregoing description of Fig. 2. The receiver 26 is operatively coupled by means of repeater coils 28 and 28 as in Fig; 3.

Fig. 5 shows another embodiment of the invention as a receiving system which does not differ in principle from those shown in Figs. 3 and 4. Its specific dillerence from the structures illustrated in Figs. 3 and 4 consists in coupling the oscillation circuits 35and 35', corresponding to the oscillation circuits 25 and 25 of Fig. 4, to the antenna I branch 3l by means of coupling coils 38 and 39 instead of to the parallel branches 32 and 33. The operative connection of receiver 26 to said oscillation circuits 35 and 35 is identically the same as that shown in Figs. 3and 4. The antenna system shown in Fig. 5 has two degrees of freedom by virtue of the parallel branches 32 and 33 and therefore there are two frequencies to which said antenna system is resonantly responsive. One of said frequencies is adjusted by tuning to coincide with the frequency of the signals to be received and oscillation circuit 35 is tuned to this same frequency. Oscillation circuit 35 is tuned to the other of said frequencies of the antenna system. As heretofore stated, oscillation circuits 35 and 35' are made to have the same damping factors by giving suitable values to the resistance elements 37 and 37 and are loosely coupled to the antenna 1. The operation of the system in eliminating interference, particularly that due to natural disturbance will be understood from the description and explanation hereinbefore given. This arrangement is preferable to that shown in Figs. 3 and 4 in that both oscillation circuits are excited by the same impulsive current in the antenna upon the incidence of astatic disturbance, and, therefore, the relative magnitudes of the natural oscillations set up in oscillation circuits 35 and 35 are invariable.

What is claimed is:

1. In a wireless duplex system, the combination of a transmitting branch circuit, a receiving branch circuit, an auxiliary branch circuit, a receiving device connected to said receiving branch circuit and said auxiliary branch circuit, and means for rendering said receiving device unresponsive to interfering oscillations of saidcircuits.

2. A wireles duplex. system comprising a transmitting branch circuit, a receiving branch circuit, an auxiliary branch circuit,

a translating device connected to said re-- circuit; and a receiving device differentially.

connected to both ofsaid detectingdevices, said oscillation circuits including electrical constants of such values that the said receiving-device is practically unaffected by oscilfirst of said branch circuits offering a low impedance to currents of the transmission frequency and a high impedance to currents of the reception frequency, the second of .said branch circuits offering a high impedance to currents of the transmission frequency and being adjusted for maximum response to the signals to be received, the third of said branch circuits offering a high impedance to currents of both said frequencies; an oscillation circuit connected to said second named branch circuit; a second oscillation circuit connected to said third named branch circuit; a detecting device connected to said second named branch circuit through said first named oscillation circult; a second de tecting device connected to said third named branch circuit through said second named oscillation circuit; and a receiving device differentially connected to both said detecting devices, said oscillation circuits including electrical constants of such values that said receiving device is practically unaffected by transmission currents and natural oscillations.

5. A wireles duplex system resonantly responsive to two frequencies, one of said frequencies being the frequency of the signals to be received and the other of said frequencies being that of the transmitted signals, said system comprising an antenna;

three parallel branch circuits through which said antenna is connected to ground, the first of said branch-circuits being substantially resonant to currents of the transmission frequency and substantially anti-resonant to currents of the reception frequency, the second of said branch circuits being substantially anti-resonant to currents of transmission frequency, and the third of said branchcircuits being substantially anti-resonant to currents of both said frequencies; an oscillation circuit connected to said second named branch circuit; a second oscillation circuit connected to said third named branch circuit; a vacuum tube detector connected to said first named oscillation circuit; a second vacuum tube detector connected to said second named oscillation. circuit; a vacuum'tube amplifier connected through said first named detector to said first named oscillation circuit; a second *vacuum tube amplifier connected through said second named detector to said second named oscillation circuit; and a receiving device difierentially connected to both of said amplifiers, said oscillation circuits including electrical constants of such values that said receiving device is practically unaffected by said transmission currents and by natural, oscillations of said system as a Whole.

6. A wireless duplex system resonantly responsive to two fre uencies, one of said frequencies being the nals to be received and the other of said frequencies being that of the transmitted signals, said system comprising an antenna;

three parallel branch circuits through which said antenna is connected to ground, the first of said branch circuits being substantially resonant to currents of the transmission frequency and substantially anti- 1 resonant .to currents of the reception frequency, the second of said branch circuits being substantially anti-resonant to cur rents of transmission frequency, the third of said branch circuits being substantially anti-resonant to currents of both said frequencies; an oscillation circuit containing resistance, inductance and capacity elements, said oscillation circuit being inductively coupled to said second and third branch circuits and being tuned to the frequency of reception; a second oscillation circuit containing resistance, inductance and capacity elements, said second oscillation circuit being inductively coupled to said second and third branch circuits and being tuned to the frequency to which said third branch circuit is responsive; a vacuum tube detector connected to said first named oscillation circuit;

a second vacuum tube detector connected to said second named oscillation circuit; a vacuum tube-amplifier connected through said first named detector to said first named oscillation circuit; a second vacuum tube amplifier connected throughsaid second named detector to said second named oscillation circuit; and a receiving device differentially connected to both said amplifiers.

7. A wireless system comprising an anrequency of the sigtenna circuit having parallel branches, two

oscillation circuits each coupled to both of said branches, a detecting device connected to one of said oscillation circuits, a second detecting device connected to the other of said oscillation circuits, and a receiving device difierentially connected to both of said detecting devices, said oscillation circuits including electrical constants of such values that the said receivin device is practically unaffected by oscillations other than those it is desired to receive.

8. A wireless duplex system comprisin an antenna; a transmitting, a receiving, an

an auxiliary branch circuit through which said antenna-is connected to ground; an oscillation circuit coupled to both said receiving branch circuit and said auxiliary branch circuit; a second oscillation circuit coupled to both said receiving branch circuit and said auxiliary branch circuit; a detecting device connected to said first named oscillahave signed my name to this specification in the presence of two subscribing witnesses, this 30th day of September, 1915.

, JOHN MILLS. Witnessesz' A. W. HAVENER, C. E. MORGAN.

In testimony whereof, I, J 015m B. CARsoN,

have signed my name to this specification in the presence of two subscribing witnesses, this 2d day of October, 1915.

JO N R. CARSON. Witnesses: 1

GEORGE E. FOLK, Fmnox S. ROBINSON. 

